The invention relates to a configuration and a method for making electrical contact between a flexible printed circuit board disposed on a supporting element and a contact spring which is pushed onto the flexible printed circuit board in a direction running parallel or obliquely with respect to the surface of the printed circuit board.
If contact with a flexible printed circuit board can only be brought about by laterally xe2x80x9cpushing onxe2x80x9d a spring contact of a component onto the printed circuit board owing, for example, to limitations of installation space or structural space or because of mounting conditions which are predefined by the configuration, there is the risk of slipping, displacement, twisting or displacement of the flexible printed circuit board by the contact-making operation. Furthermore, owing to the high degree of surface sensitivity of a flexible printed circuit board it is not always easy to manufacture such a xe2x80x9cpush-onxe2x80x9d spring contact on a flexible printed circuit board without damaging it. In particular in cases in which a high pressing-on force of the spring contact onto the flexible printed circuit board is required, the two aspects of positional stability and freedom from damage of the flexible printed circuit board during manufacture of the xe2x80x9cpush-onxe2x80x9d spring contact can be ensured only with difficulty.
Application examples of such a push-on spring contact of a flexible printed circuit board under difficult conditions are found in motor vehicle construction. Owing to the restricted amount of space, electrical components (for example solenoid valves in a hydraulic assembly of a transmission) must sometimes be electrically coupled to a flexible printed circuit board in the fashion described by a push-on spring contact. Owing to the high degree of thermal and mechanical stresses in a motor vehiclexe2x80x94vibration accelerations of up to 33 g can occurxe2x80x94high pressing-on forces must be applied for contact to be reliably formed.
It is already known to advantageously influence the frictional characteristics and reduce the risk of damage during the contact-making step by plating the contact-making elements (i.e. spring contact and conductor track) with tin.
German Patent DE 41 10 386 C2 discloses a configuration for making electrical contact with a flexible printed circuit board which is disposed in a supporting element and in which a contact spring is pushed onto the flexible printed circuit board in a direction running parallel to the plane of the printed circuit board. In order to protect against damage, a sliding element, on which the contact spring slides when it is pushed into its end position, is disposed on the supporting element so as to be incapable of being displaced.
In a further known contact-making configuration (see Published, Non-Prosecuted German Patent Application DE 27 26 231 A1) contact is made with conductor tracks of a flexible printed circuit board by crimp contacts which slide along contact springs when the flexible printed circuit board is plugged into a housing of a plug-type connector.
Published, European Patent Application EP 0 969 557 A1 discloses a contact configuration for connecting a flexible printed circuit board to a contact spring, the flexible printed circuit board having a reinforcing layer underneath at the end onto which the contact spring is pushed.
It is accordingly an object of the invention to provide protection against folding and displacement for a flexible printed circuit board in a contact-making region that overcomes the above-mentioned disadvantages of the prior art devices and methods of this general type, which permits contact to be made with the flexible printed circuit board without difficulty. In particular, the intention is that even when high pressing-on forces are required, the positional stability and freedom from damage of the flexible printed circuit board will be ensured.
With the foregoing and other objects in view there is provided, in accordance with the invention, a configuration for making electrical contact between a flexible printed circuit board disposed on a supporting element and a contact spring which is pushed onto the flexible printed circuit board in a direction running parallel or obliquely with respect to a plane of the printed circuit board. The configuration contains a sliding element disposed between the flexible printed circuit board and the contact spring so as to be incapable of being displaced with respect to the supporting element and on which the contact spring slides into an end position when pushed on.
Accordingly, the basic idea of the invention consists in providing, by the sliding element being disposed between the contact spring and the flexible printed circuit board, a device which absorbs a component of the displacement, sliding or twisting forces and which runs parallel to the plane of the printed circuit board. This prevents the forces that are exerted by the contact spring during a push-on contact-making operation from being able to act on the printed circuit board, ensuring the positional stability and freedom from damage of the printed circuit board.
One preferred embodiment of the invention is characterized by the fact that the sliding element is supported on a contact-making housing mounted on the supporting element, and is secure against displacement. In addition, or alternatively, the sliding element can, however, also be secured against displacement by attachment elements, for example claws or the like, which are disposed on its side facing the supporting element and interact directly with the supporting element.
The sliding element is preferably embodied in the form of a dimensionally stable metal tongue that has a run-in slope in the front region. When the contact spring is pushed onto the slide element, it slides into its end position, the run-in slope minimizing the initial pushing-on force required to bend the spring contact.
A first possibility is that the contact spring rests on the sliding element in its end position, i.e. the electrical contact between the contact spring and printed circuit board is made by the sliding element. Alternatively, according to a second possibility, it can, however, also be provided that the sliding element is shaped in such a way that it extends as far as a contact point provided on the flexible printed circuit board, the contact spring coming to rest in its end position directly on the contact point of the flexible printed circuit board. In this case, the sliding element serves as a pushing-on aid and can be removed after the contact-making operation has taken place.
The configuration according to the invention can advantageously be used when making contact with an electrical component, for example a solenoid valve of a hydraulic assembly of a transmission, in a motor vehicle. It has become apparent that the protection against folding and displacement according to the invention permits contact to be made in a fashion that is reproducible and free of damage while the pressing-on forces of the contact spring are sufficiently high.
In accordance with an added feature of the invention, the contact-making housing has a stop element running at a distance from the supporting element and serves to deflect the contact spring in a direction of the supporting element.
With the foregoing and other objects in view there is further provided, in accordance with the invention, an assembly, containing an electrical component of a motor vehicle, a supporting element, a flexible printed circuit board mounted on the supporting element, a contact spring connected to the electrical component, and a sliding element disposed between the flexible printed circuit board and the contact spring so as to be incapable of being displaced with respect to the supporting element and on which the contact spring slides into an end position when pushed on.
With the foregoing and other objects in view there is additionally provided, in accordance with the invention, a method for making electrical contact between a flexible printed circuit board disposed on a supporting element and a contact spring. The method includes mounting a sliding element on the flexible printed circuit board so as to be incapable of being displaced with respect to the supporting element; and pushing the contact spring in a direction running parallel or obliquely with respect to a plane of the flexible printed circuit board, in such a way that the contact spring is guided into an end position by the sliding element.
In accordance with a further mode of the invention, there is the step of forming the sliding element as an electrically conductive sliding element and after the contact spring is pushed into the end position, the sliding element remains between a contact point on the flexible printed circuit board and the contact spring.
In accordance with another mode of the invention, there is the step of removing the sliding element after the pushing on of the contact spring into the end position.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in protection against folding and displacement for a flexible printed circuit board in a contact-making region, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.